A drag rotation shaft is used for unfolding and folding an electronic device, however, the resistance provided by the drag rotation shaft is constant, that is, the resistance provided by the drag rotation shaft remains unchanged regardless of the unfolding angle of the electronic device. Although the resistance provided by the drag rotation shaft can hold the electronic device and allows the electronic device to be unfolded at any angle, a variable resistance is required to provide a hand feel for a user corresponding to various application circumstances. Further, different resistances can provide different supporting forces for the electronic device, which facilitates the user choosing a corresponding support force. Unfortunately, the conventional electronic device cannot provide a drag rotation shaft having a variable resistance.